1. Field of the Invention
The present invention relates to a display device using external light and, more particularly, to a display device using natural light or illumination light as a light source to improve visibility without greatly changing the structure of an existing display device.
2. Description of the Related Art
With the development of communication and display technology, a number of portable terminals have recently been developed. Examples of portable terminals include personal digital assistants (PDAs), portable multimedia players (PMPs), and digital multimedia broadcasting (DMB). Since liquid crystal displays (LCDs), a type of light receiving flat displays, cannot emit light by themselves, they produce an image by selectively transmitting illumination light radiated from a light source onto each pixel. To this end, backlight units are installed at a rear side of the LCDs.
Backlight units are classified according to the arrangement of light sources into a direct type and an edge type. The direct light type is configured such that a plurality of light sources are installed under an LCD to directly emit light onto a liquid crystal panel. The direct light type is suitable for large screen display devices, such as LCD TVs larger than 30 inches, since the light sources can be freely and effectively installed over a wide area. The edge light type is suitable for displays of portable terminals since a light source should be installed at a sidewall of a light guide panel.
Portable communication terminals are used in a wide variety of locations, and are often used in sunny outdoor conditions where the screen may be too dark to see, thereby decreasing the visibility of the display and reducing the portability of the portable communication terminals.